Lamp fault detection

ABSTRACT

A fault detection apparatus for a public lighting system has a number of lamps. Each lamp incorporates an operating and control circuit which will emit signals on a fault occurring or conditions arising indicating a potential fault, for example, of a gas discharge tube forming part of the lamp. The apparatus, which can be incorporated in the lamp operating and control circuit or be provided as a separate plug in unit incorporates a host interface. A control unit and an externally visible signalling device such as a flag or flashing beacon will allow the detection of a fault or potential fault for example during normal daylight hours.

FIELD OF THE INVENTION

The present invention relates to a fault detection apparatus for apublic lighting system of the type having a plurality of lamps, eachlamp including an operating and control circuit incorporating faultdetection signalling for various portions of the operating and controlcircuit.

BACKGROUND OF THE INVENTION

Essentially the term ‘public lighting system’ is used here to encompassnot exclusively public lighting per se as would be considered to be themeaning of it, but lighting systems for installations whether they beindustrial premises, government installations, sporting arenas or thelike generally extensive areas, all of which tend to have a large numberof lamps operating. Most such lamps have as their source of luminescencea gas discharge tube and this latter term is used to describe the actualsource of the light flux in the lamp but obviously other sources couldbe used.

In this specification the term “fault” is used to indicate an actualfault which causes failure of the system, a fault which causesinefficient operation of the system or indeed an imminent fault thathasn't as of yet caused any serious malfunction of the system, but whichhas produced a condition in the system which indicates the possibilitythat such a fault may arise.

Inevitably lamps fail either due to the simple wearing out of the gastube or some other failure in the operating and control circuit. Indeedlamps regularly fail prematurely due to incorrect power supply eithercaused by mains faults or, for example, faulty ballasts or igniters inthe operating and control circuit.

Additionally, the lamps often suffer, as they get older, from cyclingwhich causes the lamp to flicker on and off before failing completelyand this is an exceedingly undesirable situation to occur.

There are many available lamp control circuits at present, such as, forexample, described in European patent Specification No. 0 582 287(Smeasit S.r.l.). This specification describes an internalauto-diagnostics program for a lamp operating a control circuit, whichby means of a modem or radio link reports detected faults to anoperations centre. While similar systems are known which provide evenadjustment for individual lamps in certain situations, all the systemsto date require some form of central host processor which collects andidentifies the faults such as that of this European specification. Thisis relatively complex and expensive and is not suitable forretro-fitting.

SUMMARY OF THE INVENTION

What is needed is some relatively simple system or apparatus, wherebymaintenance personnel can be alerted to the failure or imminent failureof individual lamps. Ideally, such apparatus should be able todiscriminate between the types of failure. For example, the fault couldoccur in a ballast, which fault would need to be rectified, but wouldnot need to be urgently rectified, while the failure of a bulb or thecycling of a lamp must be rectified as quickly as possible.

Unless some elaborate detection system for faults is incorporated in thepublic lighting system such as described above the only way of detectingan actual failure of a lamp is by visual inspection of the lamp when itis operating. Potential or imminent failure can only in thesecircumstances be detected by physically testing the operating andcontrol circuits in situ on a regular basis. The former is extremelyexpensive to do, but must be done, while the latter though not essentialand costly is often necessary as neglect is even more costly.

Thus, there is a need for an apparatus which will allow a fault to beeasily efficiently detected at times which are suitable for suchdetection. Further such an apparatus should be easily incorporated inexisting public lighting systems.

Further, there is a need for an apparatus which will allow the fault tobe readily easily detected at times that are suitable for suchinspection.

According to the invention there is provided a fault detection apparatusfor a public lighting system of the type having a plurality of lamps,each lamp including an operating and control circuit incorporating faultdetection signalling for various portions of the operating and controlcircuit characterised in that the fault detection apparatus comprises:

a host interface for connection to the lamp operating and controlcircuit for the reception of fault detection signals;

a control unit for reception of the fault detection signal; and

an externally visible signalling device connected to the control unitand operable by the control unit to signal the fault.

The invention provides that the signalling device may be a flag or asignalling beacon. Both of these have their advantages. The use of aflag is simple, it is a well known piece of apparatus that is used onmany types of switchgear and can be easily seen. However, beacons haveother advantages in that they are more clearly visible and can beoperated in such a way as to attract attention, such as, for example, bycausing them to flash on and off. Thus reporting of a fault does notnecessary have to be reported by somebody solely allocated this task,but may, for example, be made by other employees or simply the generalpublic.

Ideally there is provided additional signalling means for sending thefault detection signal to a host control station, which signalling meanscan provide a short range radio signal for sending the fault detectionsignal to a remote but relatively near host station.

Indeed the host station does not have to be a central host station, butcan be a hand-held device. Thus, for example, maintenance personnel orother employees travelling in a particular area can query detectionapparatus within a local area to ascertain whether any are showing afault or not. The advantage of this is that such a signalling means andassociated hand held device need only be fitted to and used withselected lamps in a system which lamps can be chosen depending on theirrelative importance to the overall lighting system.

In one embodiment of the invention, the fault detection apparatus ishoused in a separate plug in unit for connection to the lamp. Thisallows for retro-fitting.

Ideally the control unit includes analysis means for fault detectionsignals to identify a particular fault and to cause the signallingdevice to emit a signal indicating the said fault. The advantage of thisis that maintenance personnel can be alerted to the seriousness of thefault or potential fault. In certain cases this might require immediatemaintenance attention such as the replacement of the lamp, while inother cases it might be possible simply to note the fault or imminentfault and to plan some routine maintenance.

In another embodiment of the invention the control unit includes meansfor deactivating the lamp in response to the identification of a fault.The advantage of this is that if the fault is serious then automaticallythe lamp can be deactivated such as, for example, a lamp that iscycling.

The control unit may incorporate an oscillating circuit or anopto-coupler, both of these are suitable ways of operating the device.

Ideally the signalling device is a high intensity light source, whichmay, for example, emit a coloured light which can change depending onthe fault identified. There are obvious advantages to these.

The control unit includes an additional indicator lamp to signal correctoperation of the circuit and the signalling device. The advantage ofthis is that routine inspection will show if by any chance the faultdetection apparatus is inoperative.

Ideally the control unit includes additional control means to onlyoperate the signalling device during certain times. There is absolutelyno point in having the signalling device operating in many instancesthroughout the night and only needs to be operated when people can seeit, or are likely to be inspecting it.

Similarly, in one embodiment the control unit includes light sensors tocontrol the level of light during which the signalling device operates.Again this just merely means that the time in which, for example, abeacon can be illuminated is controlled and thus there is no wastage ofpower. Indeed in relation to this ideally the signalling means operatesin a low power mode.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from the followingdescription of some embodiments thereof, given by way of example onlydescribed with reference to the accompanying drawings in which:

FIG. 1 is a functional block diagram of the invention;

FIG. 2 is portion of an operating and control circuit for a gasdischarge lamp;

FIGS. 2(a) to 2(d) are enlargements of the similarly identified portionsof FIG. 2;

FIG. 3 illustrates a further part of the operating and control circuitfor the lamp incorporating fault detection apparatus according to thepresent invention;

FIGS. 3(a) to 3(d) are enlargements of similarly identified portions ofFIG. 3;

FIG. 4 is a diagrammatic view of an another embodiment of the invention;and

FIG. 5 is a diagrammatic view of a still further embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings and initially to FIG. 1 there is illustrated afault detection apparatus, indicated generally by the reference numeral1 and a lamp indicated generally by the reference numeral 2 forming partof a public lighting system. The lamp 2 comprises a lamp operating andcontrol circuit 3 and a gas discharge tube 4.

The fault detection apparatus 1 comprises a host interface 5 forconnection to the lamp operating and control circuit 3 for the receptionof fault detection signals. The fault detection apparatus 1 furtherincludes a control unit 6 connecting to the host interface, which, inturn, is connected to an externally visible signaling device 7. As willbe described hereinafter, the signaling device can be a conventionalflag or a signaling beacon.

A specific construction of fault detection apparatus is described insome detail below however it will be apparent that the technology tocapture, analyse and process such fault signals is readily available anddoes not require an elaborate or exhaustive description.

In operation, the lamp 2 operates in normal manner until a fault isdetected in the lamp operating and control circuit 3. When a fault,which can be an imminent fault, as mentioned above, is identified in thelamp operating and control circuit 3 a signal is sent through the hostinterface 5 to the control unit 6 which then causes the signaling deviceto emit the appropriate signal. The signaling device will, as mentionedabove, give a clearly visible signal. This visible signal can allow thedetection and recordal of faults during daylight hours when the publiclighting system is not operating. Further it does not require the use oftechnically trained or indeed specifically appointed employees, but canbe detected by concerned employees.

Referring now to FIGS. 2 and 3 there is illustrated a lamp operating andcontrol circuit 3 in detail which incorporates in It the fault detectionapparatus of the present invention.

Referring firstly to FIG. 2 and FIGS. 2(a) to 2(d), the lamp operatingand control circuit is again identified by the reference numeral 3 andthe gas discharge lamp 4 is not shown, but would be connected tocontacts 10. The mains input is indicated at 11 and as is conventionalthe mains feed is a full wave rectifier indicated generally by thereference numeral 12. The remainder of the circuit illustrated in FIG. 2is a particularly useful and innovative way of operating and controllingthe lamp and is the subject of a co-pending patent application. However,a description of this, its features and advantages are irrelevant to thepresent invention. Any well known circuitry for lamp control andoperation would be equally applicable to the present invention. Similarremarks apply to portions of the remainder of the circuit illustrated inFIG. 3. At 13 is indicated the connection between the circuit of FIG. 2and of FIG. 3. The same reference numeral appears on each drawing.

Referring now to FIG. 3 and FIGS. 3(a) to 3(d), the lamp operating andcontrol circuit 3 includes a power factor control indicated generally bythe reference numeral 14 and a pulse width modulator indicated generallyby the reference numeral 15. A lamp monitoring circuit indicatedgenerally by the reference numeral 16 is provided. As has been explainedabove the construction and layout of the lamp operating and controlcircuit 3 as described above is largely irrelevant to the operation ofthe invention except in so far as there is a lamp operation monitoringcircuit provided or at least some way of identifying or accessing easilyfault signals.

The fault detection apparatus 1 includes a microprocessor controller 20forms a host interface for connection to the lamp operating and controlcircuit 3 for reception of the fault detection signals from the lampmonitoring circuit 16 and also as a control unit to operate theapparatus. The microprocessor controller 20 is connected to anopto-coupler 21 to external contacts 22. The external contacts 22, inturn, are connected to an externally visible signalling device, notshown.

In normal gas discharge lamps, due to wear and tear over time, thevoltage across the contacts 10 rises. Typically the voltage may start at80 volts optimum and keeps rising until it reaches 120 volts when thephenomenon of cycling occurs. When this happens the gas discharge lampswitches on and off in rapid succession, which is a very undesirableresult.

In operation the lamp monitoring circuit 16 senses when the voltageacross the lamp 10 strays from a certain level, either due to the lampcycling or to some other fault on the circuit. When this happens themicroprocessor controller 20 sends a high to low signal to theopto-coupler 21 which turns on the opto-coupler 21 which in turn drivesthe externally visible signalling device. This is a relatively simpleway of carrying out the invention.

The microprocessor controller is programmed to analyse the signalreceived and to carry out the additional operation of switch-off of thelamp when the voltage exceeds some preset level.

Referring to FIG. 4, there is illustrated a fault detection apparatusaccording to the present invention, namely a plug-in fault detectionapparatus 30. The plug-in fault detection apparatus 30 incorporates acasing 31 having an I/O interface 32. Mounted in the casing 31 is ashort wave radio transmitter, only the antennae 33 of which is shown.Also included and visible on the exterior of the casing is an externallyvisible signalling device formed from a signalling beacon 34. Anindicator lamp 35 and a light sensor in the form of a photoelectric cell36 are also provided. Suitable circuitry forming a control unit andconnected to the short wave radio, the signalling beacon 34 and theindicator lamp 35 and the photoelectric cell 36 is housed within thecasing 31. The construction of such circuitry is largely optional andmany arrangements could be used to enable the invention to be carriedout. Thus the apparatus and its circuit is described by reference to itsfunction. A host station in this case a hand-held transmit/receivedevice 37 is provided.

In operation the plug-in fault detection apparatus may be fitted to anylamp control circuit having an I/O interface. The signalling beacon 34will operate on a fault being detected to provide an indication of thestatus of the lamp. The indicator lamp 35 will indicate whether theplug-in fault detection apparatus 30 is operable or not, irrespective ofwhether it is indicating a fault.

The photoelectric cell 36 is provided so as to ensure that thesignalling beacon 34 only operates under certain ambient lightconditions. Generally speaking this would be daylight, or it may bepossibly restricted to certain hours of the day. The photoelectric cell36 could be used in combination with a time clock or indeed could bereplaced by a time clock or any other timer.

The signalling beacon 34 may be so constructed as to give differentsignals depending on the fault detected such as, for example,intermittent flashing or continuous flashing. Further it is envisagedthat the signalling beacon may be so arranged as to provide lights ofdifferent colours. The signalling beacon could by use of a differentcoloured light indicate correct operation of the fault detectionapparatus instead of using a separate indicator such as the indicatorlamp 35.

Referring to FIG. 5 there is illustrated a further construction ofplug-in fault detection apparatus indicated generally by the referencenumeral 40 which has an I/O interface 41 and has an externally visiblesignalling device in this case a conventional flag 42 which can beoperated to assume three positions, two of which are shown by theinterrupted lines and identified by the reference letters (a) and (b).

In operation, for example in the position 42 this would indicate thatthe lamp was operating in the correct mode. In the position illustratedby the reference numeral 42(a) this shows a fault is imminent and in theposition 42(b) it indicates that the lamp is no longer operating.

While in the embodiments described above there has been described a hoststation in the form of a handheld device, it will be appreciated thatany central host station may be used and indeed signals could be sentdown the mains wire to a central control unit. However, a hand-helddevice could be relatively useful in that it allows gradualretro-fitting of the device according to the present invention.

While in the embodiments described above an opto-coupler is used tooperate a signalling beacon, equally the beacon may be driven by asimple capacitor arrangement.

It will also be appreciated that any other solid state orelectro-mechanical device could be used.

One of the great advantages of using a flag rather than a beacon is thatonce the flag has been operated then no further power is required untilthe flag is reset.

It is envisaged that the units would operate in a low power mode.

It will be appreciated for example that the signalling beacon may beprovided by any high intensity light source, such as Xenon lamps,halogen lamps, high intensity LEDs or similar devices.

It will be readily appreciated that depending on requirements that thefault detection apparatus of the present invention can provide arelatively unsophisticated report of a fault without any discriminationbetween types of faults, or can, using suitable programming and forexample querying devices, provide considerable information to publiclighting operators to optimise the efficiency of the operation of thesystem.

In the specification the terms “comprise, comprises, comprised andcomprising” or any variation thereof and the terms “include, includes,included and including” or any variation thereof are considered to betotally interchangeable and they should all be afforded the widestpossible interpretation and vice versa.

The invention is not limited to the embodiment hereinbefore described,but may be varied in both construction and detail within the scope ofthe claims.

What is claimed is:
 1. A fault detection apparatus for a public lightingsystem of the type having a plurality of lamps, each lamp including anoperating and control circuit incorporating fault detection signallingto signal both existing and imminent fault conditions for variousportions of the operating and control circuit characterised in that thefault detection apparatus (1) comprises: a host interface (5) forconnection to the lamp operating and control circuit (3) for thereception of fault detection signals; a control unit (6) for receptionof the fault detection signal; and an externally visible signallingdevice (7) connected to the control unit (6) and operable by the controlunit (6) to signal the fault condition.
 2. A fault detection apparatusas claimed in claim 1 in which the signalling device (7) is a flag (42).3. A fault detection apparatus as claimed in claim 1 in which signallingdevice (7) is a signalling beacon (34).
 4. A fault detection apparatusas claimed in claim 1 in which there is provided additional signallingmeans for sending the fault detection signal to a host control station(37).
 5. A fault detection apparatus as claimed in claim 4 in which theadditional signalling means provides a short range radio signal forsending the fault detection signal to a remote but relatively near hoststation (37).
 6. A fault detection apparatus as claimed in claim 5 inwhich the host station (37) is incorporated in a portable device.
 7. Afault detection apparatus as claimed in claim 6 in which portable deviceis a hand held device.
 8. A fault detection apparatus as claimed inclaim 1 in which the fault detection apparatus (1) is housed in aseparate plug in unit (30) for connection to the lamp (2).
 9. A faultdetection apparatus as claimed in claim 1 in which the control unit (16)includes means for additionally deactivating the lamp (2) on detectionof a fault.
 10. A fault detection apparatus as claimed in claim 1 inwhich the control unit (6) includes analysis means for fault detectionsignals to identify a particular fault and to cause the signallingdevice (7) to emit a signal indicating the fault.
 11. A fault detectionapparatus as claimed in claim 1 in which the control unit (6) includesmeans for deactivating the lamp (2) in response to the particular faultidentified.
 12. A fault detection apparatus as claimed in claim 1 inwhich the control unit incorporates an oscillating circuit.
 13. A faultdetection apparatus as claimed in claim 1 in which the control unitincorporates an opto-coupler (21).
 14. A fault detection apparatus asclaimed in claim 3 in which the signalling beacon (34) is a highintensity light source (34).
 15. A fault detection apparatus as claimedin claim 3 in which the signalling beacon (34) emits a coloured light.16. A fault detection apparatus as claimed in claim 5 in which thecolour changes depending on the fault identified.
 17. A fault detectionapparatus as claimed in claim 5 in which the control unit (6) includesan additional indicator lamp (36) to signal correct operation of thecontrol unit (6) and the signalling device (7).
 18. A fault detectionapparatus as claimed in claim 1 in which the control unit (6) includesadditional control means to only operate the signalling device (7)during certain times.
 19. A fault detection apparatus as claimed inclaim 1 in which the control unit (6) includes light sensors (35) tocontrol the level of light during which the signalling device operates.20. A fault detection apparatus as claimed in claim 1, wherein thecontrol unit is provided with means for measuring the voltage acrosslamp contacts and means for generating the fault signal when the voltageacross the lamp contacts strays from a certain pre-set level.